Eosin-Nigrosin is a staining technique that assesses the vitality of a sperm sample when the initial motility is less than 25%. Nigrosin increases the contrast between the background and sperm heads, making sperm easier to visualize. Eosin stains only the dead sperm, turning them a dark pink, whereas live sperm appears white. This staining technique must be performed immediately after motility is assessed using sperm from the same semen sample. Stained slides can be stored for reevaluation and quality control purposes.
